Basic provisions for organizing the construction of highways. Reference book "Handbook of basic prices for the development of technical documentation for the overhaul of building structures of buildings and structures
Similar abstracts:
Theoretical foundations of the organization of production in a road-building enterprise. Manufacturing program, the cost of marketable products and the calculation in machines and mechanisms, the calculation of depreciation and costs. Plan for cost, profit and profitability.
Analysis of the natural and climatic conditions of the construction area. Technical characteristics of the road. Placement of manufacturing enterprises and provision of construction materials. Technological scheme of complex mechanization of the pavement device.
Analysis of the natural and climatic conditions of the construction area. Determination of the duration of the work of specialized units. Designing the organization of work on the construction of pavement. Technological flow diagram for the pavement.
Calculation of the size of the pit for the building, the volume of earthworks. Complete set of machines for excavation of soil and its transportation. Calculation of labor costs and wages. Calendar plan and production technology. Calculation of material resources.
Determination of the volume of earthworks from the balance condition earthen masses and average distance of soil transportation. Planning of the complex mechanized production of works. Determination of the movement pattern and brand of the excavator for excavation.
Appointment of the dimensions of the pit for the foundation of the building. Calculation of the volume of earthworks. Selection of a set of machines for excavation. Drawing up a statement of the volume of earthworks, a calendar plan. Calculation of bottomhole parameters for a dragline excavator.
Crossing of the road in one level, development of a longitudinal profile at the approaches to the intersection for roads in two levels. Calculation of runoff from a small catchment area for a culvert. Acquisition of land for a section of the road with a length of 2 kilometers.
Characteristics of the construction area and subgrade, preparatory work. Development of schedules for the volume of earthworks; choice of production method, calculation of equipment, machinery, work force. Safety requirements and environmental protection.
Natural and climatic conditions of construction. Transport scheme for the delivery of materials. Substantiation of methods of production of work by the in-line method and calculation of the main parameters. Quality control and construction of a Gantt chart for the construction of pavement.
Transport network of the design area. Characteristics of the main branches of the national economy. Prospects for the development of the region's economy and justification for the need to build a road. Natural and climatic conditions of the design area. Vegetation.
Natural and climatic conditions for the design of a highway. Calculation of technical norms of the highway. Route plan design. Calculation of an incorrect picket. Designing a longitudinal profile of a highway. Turnback project.
Characteristics of the area of construction and operation of the highway. Calculation of the need for machines and mechanisms for preparatory work. The device of reinforced concrete pipes and the construction of a subgrade. Creation of production schedule.
The concept of estimated standards, their classification. Estimated construction cost. Calculation of indicators of the structure of estimated costs of the cost of work on the construction of subgrade and pavement, analysis of the data obtained. Contractual relations in construction.
The procedure for excavating soil in a pit, determining its overall dimensions and calculating the volume of required earthworks. Selection of a set of machines and the necessary equipment for excavation in the excavation, calculation of labor costs and wages.
Analysis of natural-climatic, soil and hydrological conditions of the road construction area. Determining the timing and scope of work. Technology and organization of pavement construction. Quality control, labor and environmental protection.
Natural stone and other road construction materials. Finishing and arrangement of roads. Technical control on the construction of logging roads. Ecological and aesthetic aspects of design and construction. Method for calculating non-rigid pavement.
LECTURE #11
Topic: "Peculiarities of construction and maintenance of local roads"
1. Organization of construction of local roads.
2.Machines and mechanisms used for the construction and repair of roads.
3.Organization of repair and maintenance of roads.
4. The project of organizing the construction of the road and the composition of the design and estimate documentation.
The organization of works on the construction and repair of roads has the following features:
Production of works over a long distance;
Uneven distribution of the volume of work along the route;
Greater dependence of road construction on climatic conditions.
Depending on the performance of technological operations for the construction of the road, there are in-line and parallel methods.
The most progressive method is the in-line one, it is characterized by uniform and continuous performance of work by specialized mechanized units. Its features are a clear organization of construction and complex mechanization.
The parallel method is characterized by the execution of work dispersed in small independent areas.
Depending on the uniformity of distribution, road construction works are divided into linear and concentrated.
Linear are characterized by a relatively uniform distribution of types of work repeating along the length of the road. These include: preparatory work, the construction of small bridges and pipes, the construction of a subgrade and low embankments, excavations, foundation and coating, and other work.
Concentrated works include the construction of large and medium bridges, the construction of high embankments and deep dredging. These works are carried out by mechanized brigades.
The main conditions for the proper organization of construction work by the in-line method is the coordination of the work of specialized construction units, taking into account the scope of work and the specific conditions of this construction. Work on the route is carried out in the following sequence:
Organization of communication, arrangement of temporary household, residential and industrial buildings;
Preparatory work;
Construction of bridges and pipes;
Execution of excavation work on the construction of a subgrade and strengthening works;
Pavement foundation device;
Coating device;
Finishing work.
For the proper organization of construction, technological maps are drawn up. They reflect the requirements of the technology of work, the sequence of their implementation, quality requirements, methods of organizing construction and technical and economic indicators.
The main production unit is the road maintenance area.
To carry out major mechanized work, special road-building and bridge-building organizations are being created. District road organizations will perform all types of work on their own and can be involved in the construction of roads in agricultural enterprises, but often the construction of local roads is carried out by the farms themselves.
With the growth of traffic density, changes in the intensity and composition of traffic on the road, it is necessary to increase its technical performance indicators. The construction of the road requires large one-time material and labor costs, which determines the need for their stage-by-stage construction. At each stage, a certain level of road performance is reached. The staged method makes it possible to make the most rational use of economic opportunities, consistently consume materials, mechanization and labor resources of individual farms.
An example of staged construction can be the construction of roads with a transitional pavement with its gradual improvement to a capital one.
When developing projects for the stage-by-stage construction of local roads, both the short-term and long-term prospects are taken into account. At the first stages, a number of elements are constructed taking into account the estimated time (width of the subgrade, slopes, curve radii, etc.), and some - taking into account the requirements of the near future (width of the roadway, clothing, etc.).
The timing and sequence of construction is determined depending on the national economic significance of the roads and the points connected by them. It is based on the payback period of investments in construction.
There is a sequence of construction. Primarily constructions include roads with large freight and passenger traffic; in the second - less important ones, the need for which is due to the prospects for the development of cargo turnover points.
Roads of the first and second stages are built at the expense of funds allocated to the road fund by all enterprises of the agro-industrial complex. The third line includes roads serving mainly domestic transportation of households and enterprises. They are built at the expense of their own resources by collective farms and state farms.
With increasing freight turnover, it is more expedient to build a cheaper road and reconstruct it in the future than to immediately build a more expensive one, which for a number of years will bring losses due to its incomplete use. On roads with low traffic volumes, which are almost all local roads, staged construction using lightweight structures and local materials is used. It is important to correctly determine the timing of the reconstruction. The duration of the stage period is set by the period during which, due to the reduction in the cost of transportation, not only the funds spent on the construction and operation of the road will be returned, but also the necessary amounts for its reconstruction will be accumulated.
Staged construction provides for the construction of culverts and subgrade, taking into account the requirements of the estimated period (15 ... For the designed dirt roads, in all cases, drainage and strengthening with additives of the roadway in difficult-to-pass areas (crossings over watercourses, low places, etc.) must be provided.
An example of stage-by-stage construction of an on-farm main (main) road can be the construction of a narrowed carriageway on it with a width of 3 ... wagons, passing oncoming traffic and serving as a reserve lane for widening the carriageway in the future.
On local roads, gravel is widely used as clothing in the staged construction process. During the construction of a gravel road, the following stages are possible:
first - installation of culverts, subgrade in hard-to-travel areas, road profiling, strengthening these areas with gravel additives. After the completion of the first stage of construction, road conditions do not yet meet the requirements of road traffic;
second- arrangement of subgrade and drainage system, strengthening of the carriageway with gravel along the entire length of the road. The road satisfies the requirements of steady traffic to a limited extent;
third- arrangement of gravel cover throughout the road, snow protection, landscaping, elements of road equipment. The road satisfies local vehicular traffic;
fourth– widening of the carriageway, improvement of the surface (asphalting, black gravel or crushed stone pavement). The road meets the requirements of modern road traffic.
Thus, stage construction is characterized by the fact that it is carried out over a long period and at each new stage, the technical and operational indicators of the road increase.
The acceptance of the finished road is carried out by a special commission with the participation of representatives of the contracting construction organization, the customer, regional authorities and other services. It should be carried out during a period of time favorable for a visual inspection of the road, taking samples of soil, building materials, cutting the pavement and testing its strength. Acceptance of roads in the presence of snow cover is unacceptable. As a result of the acceptance of the road, an act is drawn up that contains:
Brief technical specification accepted objects;
The main technical and economic indicators and their compliance with the approved project;
Data on the approval of design and estimate documentation;
General assessment of the quality of work performed;
Conclusion on the readiness of the object and the decision of the commission on its acceptance into operation.
Machinery and mechanisms used for the construction and repair of roads
All types of work related to the construction of the road are divided into preparatory, construction of artificial structures, construction of subgrade, construction of foundations and pavement and road equipment.
Depending on the type of road work, methods of their implementation, types and designs of road elements, various road-building machines and mechanisms are used.
When preparing the right of way for the construction of the road, bulldozers, brush cutters, uprooters-gatherers and rippers are used.
Bulldozers - used for uprooting small forests, shrubs, stumps and roots, cutting and moving the fertile layer of soil and soil, sealing holes and depressions, recultivating the land.
Collector brush cutters - used for uprooting and cleaning stumps, roots, shrubs and small forests.
Rippers - for loosening dense soils, removing stones, uprooting, destroying rebuilt pavements.
Scrapers - are used for removing, moving and storing the fertile soil layer, as well as reclamation of disturbed lands.
For the construction of artificial structures, universal tractor units, cranes, diesel hammers, vibratory loaders, vibratory hammers, pile drivers, vibrators, concrete mixers, etc. are used. The tractor unit has a set of equipment for driving piles, digging pits, assembling pipes and bridges and performing other works. Cranes serve for unloading and installation of elements of artificial structures.
Machines for earthworks in the construction of roads are divided into three groups: earthmoving, for soil compaction, for auxiliary work.
1. Earth-moving machines provide full mechanization of the construction of the subgrade.
Cyclic excavators (with flexible or rigid suspension of working equipment);
Excavators, continuous action (rotary, chain);
Earth-moving machines (self-propelled and trailed scrapers, bulldozers, grader-elevators).
Excavators - carry out work on excavation of soil, their loading and dumping into a dump, as well as unloading crushed stone and gravel materials.
Scrapers - for layer-by-layer development and backfilling of soil. They are used for the construction of embankments, planning areas, opening quarries. Used when moving soil up to 500 m.
Bulldozers - used for cutting and embanking up to 1.5 ... 2 m, developing slopes, backfilling trenches. Soil is moved with the help of bulldozers up to 100 m, the most economical movement is up to 30 m.
When erecting high embankments, the lower part is poured with a bulldozer, and the upper part with a scraper.
Grader-elevator - cuts the soil with a disc plow and with the help of a conveyor moves it in the direction perpendicular to the movement. They arrange embankments up to 1.5 m high from domestic reserves and develop excavations.
Graders-elevators are used with a considerable length (1 ... 3 km) in cohesive soils with low cutting resistance. Trailer and self-propelled graders are used for the construction of low (up to 1 m) embankments from side reserves, the formation of ditches and troughs, road bases and clothes, the planning of slopes of embankments and excavations.
2. Soil compaction machines:
Static action (self-propelled rollers, trailed rollers, pneumatic wheels);
Dynamic action (self-propelled and trailed vibratory rollers, rammers).
3. Machines for auxiliary work:
Excavators-planners with a telescopic boom, brush cutters, rooters, rippers, drilling cranes and drilling machines.
4. Machines used in the construction of pavements and foundations use a set of machines depending on the types and designs of pavements. The trough is arranged with the help of bulldozers, graders, scrapers. Milling cutters, mixers, distributors of cement and lime, crushed stone, gravel and sand, asphalt and concrete pavers, rollers are used for the device of the base and coating.
5. Road maintenance and repair machines include: road brushes, irons, rotary and plow snow plows, asphalt mixers, gritters, etc.
Architecture, design and construction
Highway profiles: A Cross profile; B longitudinal profile; 1 dividing strip 2 road pavement 3 reinforcement strip 4 shoulder 5 base for pavement 6 embankment body 7 transverse and longitudinal slopes 8 ditch 9 zone of concentrated work 10 natural terrain profile. Let's get acquainted with the terminology that characterizes the main structural elements of highways: cross section - cross section of the road characterizing the components of the structural ...
Chapter 17
CONSTRUCTION OF ROADS
17.1. Basic concepts, terminology, classification
Highwaya complex of structures designed for convenient, safe and year-round traffic of vehicles with calculated speeds and loads.
Structurally, the road (road) is characterized by transverse and longitudinal profiles (Fig. 17.1.).
Fig.17.1. Road profiles: BUT) Cross profile;
B) longitudinal profile;1 dividing strip, 2 pavement, 3 reinforcement strip, 4 shoulder, 5 base for pavement,
6 embankment body, 7 slopes (transverse and longitudinal), 8 ditch, 9 zone of concentrated work, 10 natural terrain profile.
Let's get acquainted with the terminology that characterizes the main structural elements of roads:
- transverse profile cross-section of the road, characterizing the constituent structural elements;
- longitudinal profile longitudinal section of the road, characterizing the constituent structural elements;
- roadway the main, operational part of the road along which the movement of vehicles is carried out;
- subgradescope of earthworks for the arrangement of the bulk part of the road;
- right-of-way (alienation) area of construction Works in the cross section of the road. This zone is allotted during the design for the entire construction complex (including the organization of construction and the prospect of expanding the road);
- dividing lineconstructive zone of the road separating opposite directions of traffic. It is not intended for operation and wears, as a rule, a decorative look;
- road clothes the main, artificially reinforced part of the roadway intended for operation;
- fortification strippart of the pavement located between the pavement and the shoulder. Serves to protect the edges of the coating in the area of increased loads;
- pavementpart of the pavement, the most structurally sound, intended for traffic;
- roadside part of the pavement, located along the boundaries of the transverse profile. The roadside is of great operational importance (stopping and parking of vehicles, pedestrian traffic, location of construction equipment during repairs, etc.;
- ditch drainage trench with calculated longitudinal slope, reinforced bottom and slopes;
- mound body the total volume of earthworks (embankment) performed during the construction of the road;
- concentrated work areafront of work of great labor intensity, concentrated on a limited area of relief.
Roads are classified according to purpose and pavement design.
By purpose, roads are divided into:
- roads general purpose.The classifier contains six categories of roads characterized by the following parameters: traffic intensity; the width of the carriageway; the number of lanes; the presence of roadsides, dividing and fortifying strips;
- urban roads are classified according to the minimum number and width of traffic lanes, the estimated speed of movement, the presence of a sidewalk. High-speed, main, local (district and city) and intra-quarter types of roads are distinguished;
- rural roads. They are divided into three categories depending on the width of the carriageway (3.5 ... 6.0 m) and the presence of shoulders.
According to the design of the road surface, the roads are divided into:
- highways with improved surface (capital and lightweight). These are asphalt-concrete, cement-concrete and block-bridge pavements;
- transitional coatings: prefabricated reinforced concrete slabs, crushed stone, soil crushed stone and slag coatings;
- lower: dirt roads reinforced with gravel, crushed stone, gruss.
- transitional coatings: prefabricated reinforced concrete slabs, crushed stone, soil crushed stone and slag coatings;
17.2. Organization of road construction works.
The sequence of construction is established based on the division of all road construction works into three periods: preparatory, main and final.
In preparatoryperiod, organizational and technical preparation of construction is carried out to ensure its deployment in the initial sections defined by the construction organization project.
In the main period, all construction work is carried out.
In the final during the period, bases and other temporary structures are being liquidated, and land is being reclaimed.
All types of road construction works are divided into:
- procurement include the preparation and storage of materials, semi-finished products and parts manufactured by construction industry enterprises (stone harvesting, asphalt concrete preparation, construction of bridges, pipes, road conditions);
- transport road materials are transported by road, rail or water transport. This group of works includes the delivery of materials and semi-finished products to warehouses, factories, intermediate bases and places of direct laying;
- construction and installation works construction of all elements of the transverse profile of roads, arrangement of road conditions, construction of buildings and road infrastructure facilities.
By uniformity and repeatability, road construction works are divided into linear and concentrated.
Linear work, the volume of which is evenly distributed throughout the facility. These include: earthworks, foundations and coatings, culverts, small retaining walls, etc.
Focusedwork of great labor intensity, concentrated on a small extent (bridges, large excavations and embankments, road junctions at several levels, high-flow culverts).
For the organization of linear work, two methods are used: in-line and separate organization. inline This method is used to carry out road construction works at all linear facilities with sufficient length. The complex in-line method provides for continuous and uniform production throughout the entire construction period. If the length of the road section is insufficient and the periods of deployment and curtailment of the flow exceed the time of its effective operation, then the work is carried out by the method separate organization in which each construction process is carried out independently.
Similarly, concentrated site work is carried out.
In the organization of construction in general, it is widespread andnon-complex in-linea method when the subgrade, small and medium-sized bridges and pipes are erected a year before the installation of the pavement by the in-line method, and the pavement is built separately (by the in-line method, not connected by a single schedule of all works).
With new road construction, as well as with reconstruction over a sufficient length, the in-line method provides for: the performance of all construction work by complex mechanized subdivisions (columns, detachments, brigades); providing them with the necessary resources, including those produced by mobile roadside installations; the movement of specialized units continuously one after another along the route of the road under construction with an established average flow rate, leaving behind a completely finished road.
The main spatial parameters of the flow are: captures, plots, maps, installation sites (depending on the type of work).
The main time parameter is the flow rate, calculated by the length of the finished road, completed per shift (the main indicator of the flow). The flow rate is set during technological design.
In the process of technological design, the most modern technologies road construction works on the basis of complex mechanization. In each specialized thread, a leading machine is provided, with which the productivity of auxiliary machines and mechanisms is linked. The efficiency of choosing a set of machines is estimated by the cost of performing a unit of measure of work (1km, 1m 3, 1v, etc.).
Features of road construction must be taken into account when drawing up calendar schedules and construction plans. They must necessarily be "attached" to the topography of the area, take into account the mobile nature of the work, supply a large number building materials, structures and products. Stroygenplans should be drawn up for various periods of construction and for all areas with specific working conditions.
17.3. Preparatory work
Preparatory work in road construction is carried out almost constantly. As one section of the road is completed, it is necessary to prepare the scope of work for the next.
The composition of the preparatory work is established in the "Project for the production of works." Approximate list of technological complexes:
- creation of a geodetic base and layout of the route;
- clearing the right of way;
- drainage and temporary dewatering;
- removal of engineering networks and demolition of buildings and structures falling into the right of way;
- arrangement of temporary roads and detours;
- arrangement of quarries and reserves.
Preparatory work can begin only after the approval of the ROW and the conclusion of contracts for land temporarily used for construction needs ( restitutes). After the construction is completed, the restitutes are returned to the land user with mandatory reclamation.
The geodetic center base is created in the form of a system of polygonometric (theodolite) traverses along the road route. Base coordinates and stakeout marks must be obtained from at least two reference points of the existing geodetic network. It is necessary to take measures to ensure the safety and stability of geodesic signs.
A route is a set of lines that determine the position of the road in the plan (longitudinal axis, edges and slope soles).).The staking of the route (restoration and fixing) is carried out as follows:
- marks along the axis of the road are restored no less than after 100 m in a straight line and 20 m on curved sections. Fastening is carried out with firmly hammered stakes and high milestones or pegs (gatehouses) with their removal outside the area of work of earth-moving equipment and indicating the distance of the callout. Picketage with firmly driven stakes with their removal outside the work strip.
- the border of the sole of the embankment is fixed with pegs every 20 ... 50 m or with a furrow;
- turn angles of the track by firmly dug corner posts (at least 10 cm in diameter and 0.5 ... 0.75 m high). The pillars are located on the continuation of the bisector of the angle 0.5 m from its top. Plates with angle parameters are fixed on the pillars;
- The right of way is fixed with poles on each side of the road axis.
Technologies for performing preparatory work do not fundamentally differ from those adopted in civil engineering.
17.3. Road bed construction
The subgrade is the main structural element of the highway and its construction (organization and technology of work) is decisive in road construction.
During the construction of the subgrade, the following technological complexes of construction works are carried out:
- detailed breakdown of road elements and foundation preparation;
- development of excavations and construction of embankments;
- soil compaction;
- final layout, strengthening of slopes.
A detailed breakdown of the subgrade and elements of structures is performed depending on the method of mechanized work and is set in the corresponding technological maps. The main marking marks are taken out on the cutoffs, and the correctness of the outline of the subgrade during the performance of work is controlled by a level, sights and additional measurements. All marks are taken out on the marking pegs. During the operation of road machines, it is necessary to ensure that the marks are maintained until the end of work on the site.
Preparation of the base for subgrade includes: removal of the fertile layer; arrangement of measures for surface drainage (creation of working slopes, drainages, drainage ditches); consolidation and replacement of weak soils. These works are mainly carried out during the preparatory period.
The development of excavations and the construction of embankments are the main scope of work in the construction of the subgrade. Depending on the terrain, the transverse profiles may have a different appearance (Fig. 17.4.).
Embankment
The construction of the embankment consists in the sequential laying of the previously developed soil with compaction. The suitability of soils for the construction of subgrade is determined by their road construction properties. The most suitable coarse-clastic, sandy and sandy soils. Clay soils are of little use or unsuitable due to their tendency to frost heaving and technological difficulties in backfilling and compaction.
The soils are backfilled in layers 0.5…1.0 m thick, depending on the type of soil and the technology adopted (in the technological map) for the production of works. immediately after backfilling, the soil is leveled and compacted by soil-compacting machines. The advantages of this method can be considered the possibility of obtaining embankments with different density characteristics and the construction of embankments from various soils.
Bulldozers, scrapers, motor graders, excavators are used for the construction of the subgrade. The choice of the leading machine depends on the height of the embankment, the type of soil and the range of its movement.
When organizing an object flow, the front of work is divided into paired grips. On the first grip, the soil is dumped, and on the second grip, compaction is carried out. The dimensions of the grips are linked to the performance of soil-compacting machines and soil moisture.
When erecting an embankment, it is necessary to take into account the change in the volume of the backfill as a result of artificial compaction (against the volume of soil in the reserve).
V n \u003d V p / K y
Where, to - coefficient of relative soil compaction in the embankment compared to its natural density in the reserve;
V n - the volume of soil in the embankment;
V p - volume of soil in reserve
When dumping the top layer, the width of the edge is increased by 0.5 m in order to accommodate a reserve of soil for subsequent planning while keeping the embankment (for self-compacting).
When compiling technological maps, it is necessary to establish schemes for the development, movement and laying of soil, indicating the height marks of the embankment for each layer, working and idle moves of the main machines, design and working geometric parameters of the subgrade.
When performing work on concentrated areas (for example, dumping soil into a wetland), work can be organized: using the “pioneer” method backfilling sand into flooded soils to squeeze out water, and then layer-by-layer carry out subsequent dumps.
excavation
The development of excavations in road construction is carried out according to two main schemes: half-fill-semi-excavation and full profile.
Shallow excavations are developed by an excavator using the “frontal driving” method immediately to the design marks.
Deep excavations are developed in a tiered way. Development is carried out in the transverse and longitudinal direction. In cross section, the excavation is divided into tiers with a face height corresponding to the design parameters of earth-moving machines (determined in the technological map). Each tier should have a berm for the passage of working vehicles and ensure the stability of the slope.
Full-profile excavations, depending on the type of soil, are developed by single-bucket or multi-bucket excavators with the soil transported by dump trucks to the reserve or to the road embankment in other areas. For the development of sandy soils, various grab buckets can be used.
The subgrade in the semi-fill-semi-dredging is carried out, as a rule, by bulldozers. Scrapers can be used for larger jobs. The bottom of the excavation is leveled by motor graders, and the slopes are leveled by slope levelers.
During the production of semi-dredging-semi-filling works, in order to avoid deformation of the subgrade, due to uneven settlement, a sharp (along the steepness) boundary between the embankment and the excavation is not allowed.
When excavating soil, it is always necessary to provide drainage facilities on slopes and slopes on each tier of excavation. Before the start of the main work, a pedestrian path and a working passage are laid along the longitudinal axis of the excavation to ensure the passage of personnel and the passage of vehicles and mechanisms involved in the work.
In the presence of solid soils, special technological documents (PPR, TK) are developed for the production of blasting. In winter, layer-by-layer loosening of frozen soils is carried out.
Compaction of dumped soils.
Soil compaction in artificially filled embankments has the following objectives:
- contributes to the improvement of soil structure and its uniformity;
- increases the stability of the subgrade;
- reduces uneven precipitation during moistening, freezing and thawing of backfill soils;
- provides the maximum possible modulus of elasticity of the upper layers of the soil, which makes it possible to reduce the required thickness of the pavement.
The creation of a stable earthwork is mandatory in all cases when the pavement is arranged immediately after the construction of the embankment and in recesses within 1.2.5 m. The value of the required density is set in the project (within 0.85 ... 0.98 of the density in natural occurrence).
Numerous experiments show that in order to obtain the most dense structure, it is necessary that the soil moisture be such that the percentage of trapped air is within 4-6%. In this case, the most durable hydration shells are formed, providing minimal filtration and the least swelling of the soil, and, consequently, the highest possible modulus of elasticity. If the humidity is lower, i.e. If the volume of pores occupied by air is higher, then a stable structure is not created and when moistened, the soil swells easily, and the more, the lower the humidity, and if the density is insufficient, on the contrary, it becomes additionally compacted and precipitates, and the modulus of elasticity in both cases falls. If moisture displaces the specified percentage of air, then the structure also becomes unstable, especially with impact compaction, and the modulus of elasticity decreases.
Soil compaction is carried out in layers (layer thickness 0.3-0.5 m), after their backfilling. The work is carried out by a link of soil-compacting machines along the grips. grip size ( L ) is installed in the PPR within 100 ... 300m.
L = P t o / 2 T h B
Where: P Productivity of the link of soil-compacting machines m 3 /hour;
t o optimal humidity retention time, sec.;
T shift duration, hours;
h ,B the size of the rolling layer.
The optimal soil moisture during rolling depends on the type of soil and is within the following limits: clay - 23 ... 28%, loam - 15 ... 25%, sands - 8 ... 14%. If the soil dries out, then watering is carried out with watering machines. Water is poured in several steps, alternating moistening with mixing by plowing or loosening. Waterlogged soils are dried (technological breaks in work are arranged).
Soil compaction is carried out over the entire width of the embankment, ensuring that the trace of the previous penetration is covered by 20-30 cm. The number of penetrations is calculated in technological maps - (from 3 to 12).
The choice of compaction method depends on the type of soil and its moisture content.
- Rolling Applies to almost all types of soils. Are used different kinds rollers: pneumatic and smooth self-propelled - for all soils; cam - for messengers; lattice incoherent detrital, lumpy, frozen. Rollers can be self-propelled and trailed, weighing from 3 to 25 tons.
- Vibration is used for non-cohesive and slightly cohesive soils (sands). Trailed and self-propelled vibratory rollers weighing 3-12 tons, vibro-compacting plates weighing 125-750 kg, vibrorammers are used.
- tamping it is used for all types of soils laid in cramped conditions, in winter, with large thickness dumps (up to 1.5 m), embankments on slopes, etc. Tampering plates are used, suspended from an excavator boom weighing 2-12 tons; diesel rammers based on the T-130 tractor; light (0.1-1.5t) pneumatic and electric rammers. When calculating the efficiency of ramming, the height of the fall of the slab is set and the number of blows is calculated.
After compaction, laboratory quality control of work is carried out.
Finishing the subgrade and strengthening the slopes.
In the process of performing the main excavation work, embankments and excavations receive a rough outline their slopes are uneven, the edges are winding, and unfinished soil remains in the excavations. To give the transverse profile the design form, special finishing and strengthening works are carried out.
Finishing includes the layout of the surfaces of embankments, excavations and reserves. To strengthening strengthening of slopes of embankments, excavations and reserves; the bottom of reserves and ditches from erosion by water and wind blowing. The leveling of the subgrade and the cleaning of the excavations to the design marks is carried out immediately after the completion of the main work by a specialized unit.
Planning sequence: mound subgrade, slopes;
notches slopes, bottom of recesses.
Leveling work is carried out by motor graders, excavators and bulldozers with attachments (slopes, blade extensions, scrapers, plows). To finalize excavations and reserves, earth-moving machines bulldozers, scrapers and dragline excavators are used.
Finishing work should preferably be carried out at optimal soil moisture, which allows the use of cut soil for backfilling depressions, its good compaction and facilitates the operation of machines.
The layout is made, starting from the lowest sections (in the longitudinal profile), to ensure drainage in the production process of the work. Motor graders can plan slopes at a ratio of 1:3 when driving directly on them. Steeper slopes are planned using the blade extension and by moving the grader blade to the side. Motor graders plan embankment slopes up to 3.5 m.
Fig.17.6. Slope planning schemes: A) excavation breakdown; B) grader movement
slope; C) Use of a blade extension.
The layout is carried out in several passages along the captures. The estimated length of the capture is 300 ... 1000m, depending on the soil and the type of planner. For large volumes of work, it is advisable to use automatic blade control systems (“Profile” -P, “Profile” -30, etc.). The operation of these systems is based on the operation of electric drives from sensors attached to the blade and moving along a stretched copy string or receiving signals from laser sensors.
Planning is rough and final. Coarse before curing the embankment; final before coating device.
After the planning or completion of the construction of artificial structures, earth slopes are fixed (strengthening works). It ensures the stability and reliability of the entire subgrade. The following shall be strengthened: slopes and roadsides of the subgrade, cones and approaches to small artificial structures, the upper part of the subgrade.
Fastening designs:
- vegetative grass cover is carried out by sowing long-term grasses or by laying a previously removed topsoil;
- planting trees and shrubs;
- sodding of slopes by laying and layers of pre-harvested turf temporarily fixed with knitting needles;
- installation of prefabricated reinforced concrete elements in the form of solid or lattice block-slabs;
- fastening of slopes with riprap of sorted stone, arrangement of stone banquets at the foot of the slopes;
- monolithic fastenings of slopes made of concrete with reinforcement;
- fastening with fascines, gabions, reinforced soil.
The type of fastening depends on the steepness of the slope, the material of the slope, weather conditions, the availability of local materials, the possibilities of mechanization, etc.
The device of special layers in the subgrade.
Additional layers and interlayers reduce moisture at various points of the subgrade, which protects the embankment from freezing and subsequent uneven settlement after thawing. Measures to reduce soil moisture must be applied when using heaving soils. Additional layers and interlayers help reduce the thickness of costly pavement layers.
Additional layers are separated by purpose:
- frost protection (heat-insulating) are used to increase the temperature of the embankment in the ice formation zone. They are made of concrete mixes with light aggregate; porous stone materials treated with binders; ash and slag mixtures. The laying of various synthetic materials gives a high effect. They are laid according to individual technological schemes.
- Draining increase the filtration coefficient of the embankment in hazardous areas (according to freezing conditions). They are arranged by backfilling and compacting coarse-grained sands, crushed stone of various fractions, sorted stone.
- Waterproofare arranged along slopes and under pavement, serve to cut off atmospheric water. They are made of waterproofing, synthetic film. Local soil is often impregnated with an organic binder (tar, liquid bitumen, oil emulsions). After impregnation, loosening is carried out, followed by rolling.
- Capillary-interrupting (anti-silting) create a barrier to the rise of capillary water. Applicable for high level ground water. The basis of the construction is a layer of draining material along which capillary rise of water is impossible. They are made in the form of a "reverse filter" of sand and gravel of various fractions.
With a close occurrence of the aquifer, sub-ditch and slope drainage is arranged with the laying of a drainage drain below the estimated freezing depth.
The device of additional layers and interlayers is carried out in the process of filling the embankment. After the layers are completed, further embankments are carried out according to the “push” method using bulldozers, since cars and earthmoving vehicles are prohibited from entering the layer until a compacted soil layer with a thickness of at least 0.5 ... 0.6 m is created.
17.4. Pavement device
Modern pavements consist of several structural layers: pavement top layer of pavement, which may consist of a wear layer and one or more bearing layers; base, which may consist of upper and lower bearing layers; additional layers for various purposes.
The natural soil base has a significant impact on the operation of the pavement as a whole and on the operation of its individual layers during the construction of the road. Therefore, it is advisable to improve the soil base different ways in order to improve it bearing capacity and ensuring the possibility of movement of working transport during the construction period.
The device of the base under the "top" layer of the coating
The range of works on the arrangement of the base under the "top" layer of the coating includes the following technological complexes:
- additional profiling and backfilling of the upper layer of the embankment body;
- arrangement of temporary access roads, storage areas for materials, exits and exits;
- improvement and additional compaction of the soil base;
- the device of additional layers and interlayers;
- construction of dividing lines;
- preparation of the "black" base.
During the construction of highways of high categories, a technological break is provided for self-compacting of the embankment. After filling the top layer of the soil base, the construction of the road is suspended and traffic is allowed with restrictions on both speeds and traffic intensity for a period of one year. During this period, the embankment gives the calculated settlement and self-compacts. In this case, the marks of the top of the embankment change in the direction of decrease. After the resumption of construction, a geodetic survey of the profile is carried out and the missing soil is backfilled with compaction to the design marks.
In parallel, work is being carried out to ensure the technological requirements for the installation of the main coating, provided for by the construction plan.
These include temporary technological sites, access roads and exits to the place where individual processes are performed by specialized flows. The device of temporary entrances is associated with the movement of a large amount of soil and the presence of a fleet of permanently operating machines for earthworks.
With additional profiling, studies of the quality of the soil are carried out and, if necessary, the top layer of the soil base can be removed and replaced, or loosened and additionally compacted, with the introduction of additives that improve the quality of the base. In the same period, some additional layers are arranged (anti-silting, heat-shielding).
If the project provides for a dividing strip with plantings of trees and shrubs, then its construction should be ahead of the laying of foundations for the coating and the coating itself. In the absence of landings, the installation of the border of the dividing strip can be carried out after the first scattering of the crushed stone base.
The crushed stone base is the main (bearing) layer of the pavement on which the coating is laid. Its purpose is load perception from road transport through the coating and its distribution on the subgrade soil. Crushed stone is poured in layers, in accordance with the project, and compacted. As a material, sorted crushed stone of various fractions is used, having a wear grade of at least I ΙΙΙ. For transitional coatings, various crushed stone and gravel can be used.
Work on the construction of a crushed stone foundation is one of the most time-consuming and is carried out in two stages.
Ι stage distribution of the main fraction of the layer and its preliminary compaction (with compression and interlocking);
ΙΙ stage distribution of wedging rubble with compaction of each fraction (joining).
The technological cycle includes the following processes:
- the first scattering of large crushed stone of the calculated fraction with a layer of 15-25 cm;
- leveling with a motor grader or bulldozer;
- compaction with rollers in several passes;
- scattering of a layer 10-15 cm thick of a finer fraction;
- leveling with a motor grader;
- compaction by rollers with watering (water consumption 15…25l/m 3 );
- placer cleavingfractions, irrigation and compaction with a water flow rate of 10…12 l/m 3 ;
The fraction sizes are related to each other as 1: 0.5: 0.3. Approximately, you can take:
1st layer 80…120mm, 2nd layer 40..60mm, 3rd layer - 10…20mm.
When compacting, rollers with smooth rollers or vibratory rollers with a mass of 6 ... 18 tons are used (depending on technological requirements). In the PPR, the size of the grip (maps), the order of crushed stone placers, the number of penetrations during compaction, the mass of rollers for each layer of rolling, the watering technology are established.
During the construction of high-speed highways, an additional one or two layers of a “black base” are arranged, designed to equalize operational loads. Structurally, these layers are made of high-strength mineral material treated with a binder.
The black base is arranged in one of the following ways:
- the mixture is harvested at the asphalt concrete plant (asphalt concrete plant) in mixing plants and delivered to the place of laying by specialized vehicles. Hot mix temperature 100…110 about C is laid by asphalt pavers and compacted by a link of rollers with smooth rollers;
- the crushed stone delivered to the place of laying is mixed at the on-site technological site with a binder and stacked. As needed, the material is consumed in the embankment. Before laying, the mixtures are heated and laid warm (80..90 about C) or cold (60..70 o C);
- the crushed stone base is laid in an embankment, impregnated with a binder (liquid bitumen, coal tar, emulsions of various compositions) and compacted in several penetrations.
The choice of one or another method depends on the adopted technology for the construction of the road, the distance of delivery of mixtures from the asphalt plant, the outside air temperature, and other reasons. You should know that the higher the temperature of the mixture during laying, the faster it hardens. At the same time, hot mixtures after hardening are more brittle and less durable.
Hot mixes are used in new construction when a high speed of paving is required. Cold mixes are preferable for repair work.
After laying the “black base”, a waterproof film of bitumen emulsion or etinol varnish is laid on it.
Asphalt technology
Asphalt-concrete pavements are most suitable for absorbing loads from road transport, are relatively cheap and simple in road construction work, and therefore are widely used for the main pavement.
Asphalt concrete mix (ABS) consists of the following components:
- rubble sorted, from igneous, sedimentary or metamorphic rocks with wear grade I-Ι...I-Ι V and strength grade 1400…500kg/cm 2 ;
- sand natural or crushed. Usually coarse and medium sands are used, clean, containing no more than 3 ... 5% of dusty, clay and silty particles;
- mineral supplementsaggregates designed to increase the strength and corrosion resistance of ABS, improve the adhesion of crushed stone with a binder and binder consumption. They are enveloped in bitumen in the contact zone, forming water-insoluble compounds that affect the strength, water and heat resistance of asphalt concrete mixtures. Additives are a powder, a product of fine grinding of limestone, dolomite, metallurgical slag and other industrial waste;
- astringent organic macromolecular compounds. They adhere well to the surface of mineral materials, have plasticity, elasticity, resistance to weathering, and are insoluble in water. The main binders include petroleum bitumen and emulsions and tars made on their basis.
Oil road bitumen is divided into viscous and liquid.
Viscous bitumen are classified by brand based on the main indicators: viscosity, extensibility and softening point. The brand is assigned according to the penetration index (the depth of penetration of a standard needle into bitumen at a temperature of 25 and 0 about C for
5 sec. under the action of a load of 100 g). Range of grades BND200/300.. .BND-60/90.
In the case of using bitumen of high viscosity, the strength and rigidity of coatings increase, less viscous bitumens increase the resistance of asphalt at low temperatures, but increase the hardening time.
Liquid bitumen obtained mainly by mixing viscous bitumen (grades BND40/60 or BND60/90) with a thinner. Liquid bitumens well envelop mineral materials, creating a thin, durable and waterproof film on their surface. The main indicator of liquid bitumen is the viscosity, determined by a standard viscometer. Grades are set according to the rate of expiration of 50 ml of bitumen at a temperature of 60 about C through a 5mm hole in the bottom of the viscometer. Range of grades: SG40/70… …MGO130/200.
The composition of the asphalt concrete mix includes by weight: 40 ... 65% crushed stone; 30…50% sand; 10…15% mineral additives and 2…10% binders. In technological design, the composition of the mixture is calculated.
Asphalt concrete mixes are hot, warm and cold.
Hot manufactured using viscous bitumen, operating temperature 170…90 about C. Technological (working) state, depending on the outdoor temperature), about 1 hour. Transportation range from 20 km (winter) to 50 km (summer). Traffic can be opened after 3..5 hours after laying and compaction.
Warm - are made using low-viscosity and liquid bitumen, working temperature 140…80 about C. Laying is carried out only at positive air temperatures. These mixtures have increased crack resistance at low temperatures. Hardening after laying lasts at least one day.
Cold - are made using liquid bitumen or emulsions. Working temperature 30…50 about C. These mixtures can be stored for up to 8 months in expendable warehouses and used as needed. Cold mixes frost-resistant, can be laid at negative temperatures (up to 50 about FROM). It takes several days for them to harden.
Machines used in the installation of coatings.
The following types of machines are used in the construction of bituminous pavements: bulldozers, motor graders, distributors of stone materials (gravel and crushed stone), watering machines, sweepers, asphalt distributors, asphalt spreaders, road rollers, bitumen boiler-spreader, machines for heating asphalt concrete pavements, dump trucks, thermal mixers and thermal profilers. The range of mechanisms is very wide. AT modern conditions rational selection of mechanization will affect the cost of the road.
Technology for laying asphalt concrete mixes
The scope of work on the installation of the main asphalt concrete pavement includes the following: technological processes:
- cleaning the base from dust and dirt with sweepers, if necessary, drying and fine backfilling;
- checking the geometric parameters of the base (width, elevations, slopes). Measurements are carried out with theodolites, levels and tape measures. Particular attention is paid to the presence of irregularities when using machines with an automatic tracking system for driving the working bodies (roughnesses should not exceed 2 mm). If the irregularities exceed the permissible values, then a leveling layer is arranged in advance on uneven places from the same material as the base, or from an asphalt concrete mixture;
- detailed marking work of pavement edges, layers, working marks along the axis of the road,
- installation of the base of the tracking system of the asphalt paver (copy string or laser system). When using asphalt pavers without a tracking system, in order to comply with the required profile and marks, immediately before laying, control beacons from the asphalt concrete mixture are set, the thickness of which should be equal to the thickness of the layer being laid in a loose state;
- bituminous emulsion primer. For strong adhesion of the asphalt layer to the base, a day before laying, watering with an asphalt distributor is carried out with a bituminous emulsion (emulsion consumption 0.6..0.9 l / m 2 );
- laying asphalt mix. ABS is laid on a solid, clean and dry base at an ambient temperature of at least 5 about C (for hot and warm mixes). At low temperatures, special laying technologies are being developed;
- ABS seal.
The supply of material (asphalt-concrete mixture) is carried out by dump trucks continuously until the end of work on the grip. With small volumes of work, ABS is poured onto the base manually, smoothed and rolled. This technology is unproductive and requires a large number of workers. Modern construction involves the use of high-performance asphalt pavers.
The work front is divided into areas and traffic lanes. The length of the grip is 100 ... 300m. The width of the paving lane is assigned to a multiple of the pavement width, taking into account the size of the paver spreaders (3-3.75m). The mixture is laid in separate short strips 25 ... 100 m in turn on each half of the width of the coating. ABS is laid according to the scheme (Fig. 17.8.).
Having laid one strip, they move to the next one until the edge of the previously laid layer has cooled down. With this technology, special attention is paid to the fact that the laying strips of the coating are conjugated, and the resulting longitudinal seams are sealed. In the places of conjugation, it is necessary to achieve complete uniformity of the coating texture during the compaction process. The position of the edge of the sealing means is ensured by the correct installation of the paver before each lane is asphalted.
Asphalt pavers can lay the mixture in a layer with a thickness of 3 ... 20 cm. pavement thickness is changed by adjusting the height of the tamper and screed relative to the paver frame. In this case, the coefficient of compaction of the mixture is taken into account.
Structural layers of ABS are laid by complex teams of 8 people. (including mechanics).
ABS sealing is the main technological operation that predetermines the physical and mechanical properties of the coating. In the process of compaction during successive passes of the roller, the mixture is deformed due to a decrease in porosity, i.e. reduction in the volume of the compacted layer. In this case, the formation of the coating structure occurs.
The compactibility of ABS is influenced by the temperature of the mixture, its granulometric composition and the accepted methods and technologies of compaction. Compaction is carried out by rolling with smooth rollers, tamping or vibration. Compaction of mixtures is carried out, as a rule, by a link of compacting machines for various purposes. Their selection, the number of penetrations, the temperature regime of the mixture, the geometric parameters of the grips are set technological maps within the PPR.
To ensure the quality of the road surface, it is necessary to organize all types of control (input, operational and acceptance)
At the input control stage, the compliance of the components of asphalt concrete mixtures with the specifications is checked.
At the place of laying (operational control), the temperature and amount of the laid mixture, evenness, layer thickness, density, strength, uniformity of asphalt pavements are constantly checked.
Acceptance control is carried out in stages of construction. All geometric parameters of the longitudinal and transverse profiles are measured, executive diagrams are drawn up, acts of acceptance of hidden works are submitted and submitted to the working commission for acceptance.
7
I = ……..
roadway
subgrade
right-of-way
Fig.17.2. Cross section of the structure
highways
6 5 4 3 2 1
1 main coating layer;
2 the bottom layer of the coating ("black" coating);
3 crushed stone preparation;
4 additional layers;
5 additional layers4
6 mound body
IN 2
IN 2
Rice. 17.3. Breakdown of the route: 1 axis of the road; 2 slope sole;
3 right of way; 4 outrigger; 5 remote stakes;
6 - pickets
°°
full excavation
moving
soil
development profile
soil replacement
backfill layers
Rice. 17.4. Types of embankments and excavations: a) an embankment on a horizontal section;
c layer thickness; b) an embankment on a weak foundation; c) excavation on a slope (semi-excavation); d) half-cut-semi-fill (with a "zero" balance of earthworks); e) full excavation
Complete profile
Half-cut-semi-fill
Fig.17.5. Approximate sequence of excavation of the soil in excavations along the grips.
one…. 6 - number of grips.
Over 3.5m
Up to 3.5m
dump
breakdown
Planning surface
Project profile
Blade extension
1:1,5
Rice. 17.7. Pavement design
1 - the body of the embankment;
2 - improved soil base;
3.4 additional layers and interlayers;
5 crushed stone (gravel) preparation;
6 the bottom layer of the coating (“black base”;
7 - the main ("top") layer of the coating.
ΙΙ
ΙΙΙ
ΙV
Rice. 17.8. Scheme of penetrations of the asphalt paver: 1…6 sequence of sections for laying the mixture; Ι-ΙV lane numbers; B the width of the road; L strip length;
shading shows the idle strokes of the asphalt paver.
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aik is linearly independent; All vectors of the system a1 a2 am are linearly inverted through ai1ai2. The basis of the space Rn is the system of vectors a1 a2 an є Rn such that the system a1 a2 an is linearly independent; The skin vector to space Rn is linearly expressed through a1 a2 an. Zvіdsi α1= α2==αn=0 linear combination is trivial and the system is linearly independent. The bountiful vector is linearly expressed through e1e2en . | |||
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In the prevіlnіy system of vectors a1a2am, all linearly independent subsystems are taken into account. The number of vectors in the fixed subsystem will be called the rank of the vector system a1 a2 am . Such a rank of a system of vectors is the maximum number of linearly independent vectors in the system. I realized that the rank of a linearly independent system is equal to the number of all vectors in the system. | |||
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The rank of the vector system a1 a2 am is called the horizontal rank of the matrix, but the rank of the matrix in rows and is assigned. The columns of the matrix A can be seen as m virtual vectors b1 b2bn with the actual coordinates of the element in the space Rm. The rank of the system of vectors b1 b2bn is called the vertical rank of the matrix A, and the rank of the matrix A after the columns and is denoted by rbA. | |||
22929. | Concept of basic minor | 15.5KB | |
Let us accept the Concept of the basic minor. Assume that Δr is a real minor to the order r of the matrix A r≤mr≤n. A minor of the order r1 of a matrix is called otochuyuchy for a minor Δr, so that a matrix can revenge the matrix of a minor Δr in itself. | |||
22930. | Foundation of the basic minor | 21KB | |
For the Δ1 minor, all possible minors are added together. For which sequence, to the minor Δ1, all possible rows and all possible columns are added. If all the singular minors reach zero, then after the signified minor Δ1 the basic and the process will end. For the minor Δ2, all possible rows and columns are added sequentially. | |||
22931. | Theorem about basic minor and її nasledki | 87KB | |
Let the minor Δr be the order of r є the basic minor of the non-zero matrix. The same rows of the matrix on which will be minor Δr linearly independent; all other rows of the matrix are linearly spanning through them. Without losing the zagalnosti mirkuvan it is possible to consider that the basic minor will be on the first line of the first r rows and r stovpchikiv matrices. It is possible to take a11 into account, otherwise, in order to prove it, it is possible to rearrange the first rows in the matrix A and, if you think about it, the theorems do not change. | |||
22932. | Matrix rank theorem | 21KB | |
For whether a matrix is horizontal or vertical, the ranks are equal and coincide with the rank of the matrix behind the minors. Tse means the order of the basic minor of the matrix is equal to k . According to the theorem about the basis minor, k rows in the matrix A on which the basis minor is linearly independent, and the lines of the rows are linearly rotated through them. | |||
22933. | Methods for calculating the arbitrators in n order | 761.5KB | |
Understanding the vyznachnik of the nth order. The numbers aіj are called elements of the signifier . Dobutok 5536 є one of the dobutkіv vyznachnik oskіlki middle yogo spіvmnіkіv є one and less than one element each from the skin line and skin stovpchik vyznachnik. Analytical note of the leader. | |||